Arkansas CDL — Air Brakes Practice Test 1

11.You keep driving after the low air warning comes on, and tank pressure keeps dropping. On a typical tractor or straight truck, around what pressure will the spring brakes come fully on?

Around 55 psi, the moment the warning comes onAround 80 to 85 psiOnly at 0 psi, once the tanks are emptyTypically between 20 and 30 psi

12.With the controlled braking method, how hard do you press the brakes?

All the way down, releasing only after the wheels lockFirmly, but short of the point where the wheels lockJust hard enough to feel a slowdown, for about three secondsLightly, letting the engine do all the stopping

13.During the walk-around, which brake lining condition is acceptable?

Firmly attached, free of oil and grease, and not worn thinLoose on the shoeSoaked with greaseWorn dangerously thin

14.You are in the proper low gear on a long downgrade and using the brakes to trim your speed. About how long should each brake application last?

About ten secondsAbout one secondAs long as it takes to reach the bottom of the gradeAbout three seconds

15.Water and compressor oil in an air brake system tend to settle in one part of each air tank. Where, and why does that matter?

At the top of the tank, where the safety valve lets them outAt the bottom of the tank, where each tank's drain valve is locatedIn the brake chambers at the wheels, where the slack adjusters push them outIn the governor, which filters them out on its own

16.You must brake hard to avoid a stalled car, and your truck's ABS is working. What should ABS let you do that locked wheels would not?

Steer around the obstacle while you are brakingAlways stop in half the usual distanceTake your foot off the brake and let ABS stop the truckBrake without watching your mirrors

17.Where is the safety relief valve installed in an air brake system?

On each brake chamber at the wheelsOn the dash, next to the parking brake knobIn the first tank that the compressor pumps air intoOn the last tank before the trailer air lines

18.When does an antilock braking system actually step in?

Every time you press the brake pedalOnly when the wheels are about to lock upOnly at speeds above 55 mphOnly when the low air warning is on

19.Your truck has automatic slack adjusters. Do you still need to check them during your inspection?

No; automatic adjusters never go out of adjustmentYes; they self-adjust when the brakes are fully applied, but they still have to be checkedOnly after the truck passes 100,000 milesOnly if the ABS lamp stays on

20.You are driving an older air-braked truck. Which of these might its parking brake control be?

A red, eight-sided knobA round blue knob or a leverA pedal to the left of the clutchA button on the steering wheel that also sounds the horn